Background/Purpose

AMPK is a master metabolic energy regulator, whose tissue activity drops in response to nutritional excesses, alcohol consumption, and in obesity, metabolic syndrome and diabetes, and high levels of soluble urate. In addition to its anti-inflammatory effects, AMPK activity promotes microtubule stabilization. Therefore, we tested the effects of AMPK activation on urate crystal-induced inflammatory responses, and the hypothesis that AMPK activation transduces the capacity of the microtubule stabilizing agent colchicine to limit gout-like inflammation.

Methods

We studied bone marrow derived macrophages (BMDMs) from AMPKα1 knockout (KO) and wild type (WT) mice, and human monocytic THP-1 cells, and assessed a low concentration (10 nM) of colchicine achieved by “low dose regimens” for both prophylaxis and treatment of gout in humans. We examined expression and phosphorylation (activation) of AMPKa and of LKB1, the major upstream activating kinase for AMPK. We also assessed negative regulators of AMPKα phosphorylation (phosphatases 2A and 2C), and parameters of NLRP3 inflammasome activation and of macrophage inflammatory M1 to anti-inflammatory M2 polarization (iNOS, arginase, respectively). We studied acute MSU crystal-induced inflammation in vivoin subcutaneous air pouches.

Results

Colchicine (10 nM) increased AMPKα and LKB1 phosphorylation in cultured macrophage lineage cells, but phosphatases 2A and 2C were unchanged. Colchicine (10 nM) enhanced protein expression of total AMPKα translationally in BMDMs. Furthermore, colchicine (10 nM) promoted macrophage polarization toward anti-inflammatory M2 phenotype by increasing ratio of arginase (M2-like) to iNOS (M1-like) mRNA expression. Colchicine partially but significantly inhibited caspase-1 cleavage and IL-1β maturation, as well as release of IL-1β and CXCL1 in response to MSU crystals in WT but not AMPKα1 KO BMDMs. Hence, manifold anti-inflammatory effects of colchicine were AMPK-dependent. Last, acute gout-like inflammation (neutrophil infiltration) were attenuated by pharmacologic AMPK activation in WT (p<0.01 compare to non-treated mice, 95% CI of difference: -5.9 to -0.9), but were enhanced in AMPKα1 KO mice (p<0.001 compared to WT mice, 95% CI of difference: 1.6 to 5.6) in vivo. 

Conclusion

AMPK transduced multiple low dose colchicine anti-inflammatory effects in vitro, including promotion of M2 macrophage polarization, inhibition of NLRP3 inflammasome activation and reduction of IL-1β and CXCL1 release. Moreover, AMPKα1 knockout significantly enhanced model acute gout-like inflammation. Our results reveal a novel molecular mechanism of action for colchicine, and suggest that decreased AMPK activation triggered by certain nutritional excesses and co-morbidities may heighten the inflammatory potential of deposits of urate crystals. Hence, colchicine, and other pharmacologic AMPK activators currently in the clinic for other conditions (methotrexate, salicylates, high dose aspirin, metformin), may have the potential to enhance efficacy of anti-inflammatory prophylaxis and treatment of gouty inflammation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/low-dose-colchicine-anti-inflammatory-effects-are-transduced-by-amp-activated-protein-kinase-ampk/